Circuit-interrupting system



L. W. CHUBB.

CIRCUIT INTERRUPTING SYSTEM.

APPLICATION FILED JULY 28. 1917.

1 ,370,004. Patented Mar. 1, 1921..

' WITNESSES: I INVENTOR 2;? 7% Law/s my ATTORNEY UNITED STATES LEWIS W. fi UBB, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTBIC 1i MANUFACTURmG GOMPANY, A CORPORATION OF PENNSYLVANIA.

' I cmcurr-mnnnurrme SYSTEM.

' Specification of Letters Patent.

Patented Mar. 1, 1921.

Application filed July 28, 1917. Serial No. iaaaco.

To all whom it may concern: I

Be it known that I, Lnwrs W. Grimm, a; citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Circuit- Interrupting Systems, of which the following is a specification.

My invention relates to circuit-interrupting systems and particularly to means for, and methods of, automatically interrupting alternating-current circuits, under predetermined conditions.

One object of my invention is to provide means for maintaining the arc in an asymmetric valve and for so neutralizing the current traversing the valve, under predetermined conditions, that the 'arc shall be extinguished.

Another object of my invention is to provide a system of the above indicated character that shall be simple to connect and effective in its operation.

In practising my invention, I provide .two transformers that are connected across the circuit to be protected. Asymmetric valves are connected between the corresponding terminals of the transformers, and a source of-direct current is connected between the mid points of the transformers. The direct current, that is supplied, traverses the valves in parallel and its potential is of such value that the current traversing each valve is equal to the maximum value of the overload current that is desired to be permitted to traverse the circuit. That is, the direct current maintains the arcs in the valve until the alternating current in one valve is equal to, and opposite in sign to, the direct current. Under this condition, the arc in one of the valves is extinguished. When the arc in one of the valves is extinguished, the direct current through the other valve is increased to double the value of the alternating current in the circuit and, because of this two-to-one ratio, it will change at double its normal rate and reach zero at the same time that the alternating current does. Thus, when the current in the valve reaches zero, its arc will be on tinguished and the circuit will be interrupted. I

In the accompanying drawings, Figure 1 is a diagrammatic view of an electric circuit embodyingmy invention and Fig. 2 is a diagrammatic view of an electric circuit em-. bodying, a modified form of my invention.

In Flg. 1 of the drawings, the primary.

winding 1 of a transformer 2 is connected, through a circuit interrupter 3, to a source of energy (not shown). One terminal of the secondary winding 4: of the transformer 2 1s connected to the anode 5 of an asymmetrlc valve. 6 the cathode 7 of which is connected to one terminal of the primary wind ng 8 of a transformer 9, the secondary winding lOof which is connected to a load (not shown). The other terminal of the secondary winding 1 of the transformer 2 is connected to the anode 11 of an asym metric valve 12 the cathode 13 of which is connected to the other terminal of the primary wmding 8 of the transformer 9. A circuit 14, comprising a trip coil 15, a source 16 of direct-current electromotive force, a resistor 17 and a switch .18, is connected between the mid point 19 of the winding 4: and the mid point 20 of the winding 8. The trip coil 15 is adapted to hold the interrupter 3 in its closed position against the actlon of a spring 21 when current traverses the circuit 14 and is adapted to permit the circuit interrupter 3 to be tripped when no current traverses the circuit 14.

In order to complete the circuit from the source of energy to the load, the switch 18 is closed to'cause direct current to traverse the valves 6 and 12 in parallel when the arcs in the valves are set up by any of the well known arc-striking means (not shown). The resistor 17 is adjusted until the current that traverses the valves 6 and 12 is equal in value to the instantaneous value of the alternating current that is to be permitted to traverse the circuit. The circuit inten rupter 8 is next closed and alternating current traverses the valves 6 and 12 and the transformers 2 and 9 to thereby effectively complete the circuit from the source of energy to the load.

If the alternating current traversing the circuit exceeds a predetermined overload value which is greater than the value of the direct current traversing the valves, it will neutralize the direct current traversing one of the valves to thus extinguish the arc in the same. When the arc in one of the valves is extinguished, the direct current through the other valve is double the value of the alternating current in the circuit and, be-

cause of this two-to-one ratio of transformation, it will change at double the rate and reach zero at substantially the same time that the alternatin current does. When the current in the va ve reaches Zero, the arc is extinguished and the circuit is interrupted. When the arcs in the valves 6 and 12 are interrupted, no current traverses the circuit 14 and, consequently, the spring 21 effects the opening of the circuit interrupter 3.

In Fig. 2 of the drawings, a circuit 22 is connected between the mid point 23 of an auto transformer 24 and the mid point 25 of an auto transformer 26 that are connected across a circuit 27 to be protected. The asymmetric valve 6 is connected in one conductor of the circuit 27 and the asymmetric valve 12 is connected in the same direction in the other conductor thereof. The circuit 22 comprises the source 16 of direct-current electromotive force and the switch 18. The circuit interrupter 3 is provided with a novoltage trip coil 28 that is connected in shunt relation to the load end of the circuit 27.

lVhen it is desired to close the circuit 27, the switch 18 is closed to permit the arcs in the valves 6 and 12 to be established by any well known arc-striking means (not shown) which may then be disconnected. After the arcs are established, the circuit interrupter 3 is closed to permit the alternating current to traverse the circuit. In this modification of my invention, the direct current supplied by the source 16 of electromotive force has a value equal to the maximum value of the overload current to be permitted in the circuit and is adapted to be successively neutralized by the alternating current traversing the valves 6 and 12 to extinguish the arcs and thereby interrupt the circuit. However, when the valves 6 and 12 are rendered inoperative, the voltage across the load end of the circuit 27 is reduced to zero and the spring 21 is adapted to trip the circuit interrupter 23 to thus more effectively open the circuit.

Since the direct-current voltage that is supplied to the valves 6 and 12 is suppled to both portions of the transformer in the opposite direction, no voltage is induced by the same in the transformer and, conse quently, the current through the valves is limited by the drop in potential across the valves and the resistance in the circuit only. In order to change the overload setting of the system, it is only necessary to vary the direct current traversing the circuit. Of course, this value of direct current must always be suflicient to maintain the arc in the valves otherwise they will be extinguished when the alternating current passes through its zero valve.

It will be understood that the transtion as transformers since it is only necessary to provide balancing inductors to permit the equal division of the direct current.

I do not limit my invention to the particu-- lar devices illustrated, as many modifications may be made therein without departing from the spirit and scope of the invention, as set forth in the appended claims.

I claim as my invention:

1. In an alternating-current circuit, the combination with two inductors, connected across the circuit, of asymmetric valves connected between the inductors, and a source of direct current connected between the mid points of the inductors.

2. In an alternating-current circuit, the combination with two inductors connected across the circuit, of asymmetric valves connected between the inductors, and means for causing a direct current to traverse the valves that shall be equal in value to the instantaneous value of the maximum alternating current that is desirable to permit to traverse the circuit.

3. In an alternating-current circuit, the combination with an asymmetric valve therein, of means for causing a direct current to traverse the valve that shall be equal in value to the value of the maximum instantaneous alternating current that is desirable to permit to traverse the circuit.

4. In an alternating-current circuit, the combination with an asymmetric valve connected in each conductor of the circuit to permit the alternating current to traverse the circuit, of means for so normally causing a direct current of a predetermined value to traverse the valves that, when the instantaneous value of the alternating current equals the direct current traversing the valves, the circuit will be interrupted.

5. In an alternating-current circuit, the combination with a vacuum-electric valve connected in each conductor of the circuit,-

of means for causin direct current to so traverse the valves t at the circuit is normally completed, the value of the direct current being such that, when the alternatingcurrent exceeds that value, the two currents will neutralize each other to reduce the voltage across the valves to substantially zero and thereby interrupt the circuit.

6. In an alternating-current circuit, the comblnation with a vacuum-electric valve connected in each conductor of the circuit, of means for maintaining the arcs in the valves under normal conditionsand for cooperating with the 'alternatin current to extinguish the same when the a ternating current exceeds a predetermined value.

In an alternating-current circuit, the

rect current to the valves as to maintain.

the arcs in the valves under normal conditions and for cooperating with the alternating current to extin ish the same when an overload traverses t e circuit.

8. In an alternating-current circuit, the combination with a vacuum-electric valve connected in each conductor of the circuit, of means for so connecting a source of direct current to the valves as to maintain the arcs in the valves under normal conditions and for cooperating with the alternating current to successively extinguish the same when an overload traverses the circuit.

9. The method of interrupting an alternating-current circuit havin asymmetric valves therein which consistsmsup lyinga maintaining direct current to the vaFves that shall cooperate with the alternating current in the valves under predetermined conditions to extinguish the arcs in the valves.

10. The method of interrupting an alternating-current circuit having vacuum-electric valves therein that consists in sup 1ying a maintaining current to the va ves which shall be so neutralized by the alternating current under predetermined conditions as to thereby extinguish the arcs in the valves.

11. The method of interrupting an alterv for maintainin nating-current circuit having an asymmetric valve therein which consists in supplying a maintaining direct current to the valve that shall be of a value equal to the maximum instantaneous value of the alternating current that is desirable to be permitted to traverse the circuit.

12. In an alternating-current circuit, the

combination with two transformers connected across the circuit, of two asymmetric valves connected between the transformers, and a source of direct current connected between the mid points of the transformers the arcs in the valves under normal con 'tions and adapted to be neutralized by the alternating current to extinguish the arcs under predetermined conditlons.

13. In an alternating-current circuit, the combination with two transformers connected across the circuit, of two asymmetric valves connected between the transformers, and a source of direct current connected between the mid points of the transformers for maintaining the arcs in the valves under normal conditions and adapted to be successively neutralized by the alternating current to extinguish the arcs when a predetermined overload traverses the circuit.

In testimony whereof I have hereunto subscribed my name this 18th day of July,

LEWIS W. CHUBB. 

